Granular electrical connections for in situ formation heating

Abstract

A method for heating a subsurface formation using electrical resistance heating is provided. In one aspect, the method includes creating a passage in the subsurface formation between a first wellbore located at least partially within the subsurface formation, and a second wellbore also located at least partially within the subsurface formation. An electrically conductive granular material is placed into the passage so as to provide electrical communication between the first wellbore and the second wellbore. Electrically conductive members are provided in the first wellbore and second wellbore so as to form an electrically conductive flow path comprised of the electrically conductive members, the granular material, and a power source. An electrical current is established through the electrically conductive flow path, thereby resistively heating at least a portion of the conductive members which in turn heats the subsurface formation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of pending U.S. provisional patent application Ser. No. 60 / 919,391, which was filed on Mar. 22, 2007. That application is titled “Granular Electrical Connections for In Situ Formation Heating” and is incorporated herein in its entirety by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to the field of hydrocarbon recovery from subsurface formations. More specifically, the present invention relates to the in situ recovery of hydrocarbon fluids from organic-rich rock formations including, for example, oil shale formations, coal formations and tar sands formations. The present invention also relates to methods for heating a subsurface formation using electrical energy.[0004]2. Background of the Invention[0005]Certain geological formations are known to contain an organic matter known as “kerogen.” Kerogen is a solid, carbonaceous material. When kerogen...

AI Technical Summary

Benefits of technology

[0019]In one embodiment, a method for heating a subsurface formation using electrical resistance heating is provided. The method may include creating a passage in the subsurface between a first wellbore located at least partially within the subsurface formation and a second wellbore also located at least partially within the subsurface formation. The method may further include placing an electrically conductive granular material into the passage to form a granular electrical connection where the granular electrical connection provides electrical communication between the first wellbore and the second wellbore. The method may further include providing a first electrically conductive member in the first wellbore so that the first electrically conductive member is in electrical communication with the granular electrical connection, and providing a second electrically conductive member in a second wellbore so that the second electrically conductive member is also in electrical communication with the granular electrical connection. In this way an electrically conductive flow path is formed from the first electrically conductive member, the granular electrical connection and the second electrically conductive member. The method may further include establishing an electrical current through the electrically conductive flow path, thereby generating heat within the electrically conductive flow path due to electrical resistive heating. At least a portion of the generated heat may thermally conduct into the subsurface formation. The generated heat may be comprised of first heat generated from the first electrically conductive member, second heat generated from the second electrically conductive member, and third heat generated from the electrically conductive granular material, with the first heat, the second heat, or both being significantly greater than the third heat.

[0020]Another embodiment of the invention includes a method for heating a subsurface formation using electrical resistance heating. The method may include providing a first substantially vertical wellbore located at least partially in the subsurface formation, and providing a second substantially vertical wellbore located at least partially in the subsurface formation adjacent the first wellbore. The method may also include hydraulically fracturing the subsurface from the first wellbore to form a first fracture, and hydraulically fracturing the subsurface from the second wellbore to form a second fracture. The method may further include injecting an electrically conductive granular material into the first fracture and the second fracture to form a first electrically conductive fracture and a second electrically conductive fracture. The method may further include providing a first electrically conductive member in the first wellbore, and a second electrically conductive member in the second wellbore. In this manner the first electrically conductive member is in electrical communication with the first electrically conductive fracture, and the second electrically conductive member is in electrical communication with the second electrically conductive fracture. The method may further include providing a fourth wellbore having a substantially horizontal bottom portion that intersects the first fracture and the second fracture. In this embodiment, a fourth electrically conductive member is provided in the fourth wellbore so that an electrical flow path is formed between the first electrically conductive member, the first electrically conductive fracture, the fourth electrically conductive member, the second electrically conductive fracture, and the second electrically conductive member. The method may then include establishing an electrical current through the electrical flow path in order to generate heat due to electrical resistive heating primarily from the first electrically conductive member and the second electrically conductive member. At least a portion of the generated heat thermally conducts into the subsurface formation so as to cause at least partial conversion of solid hydrocarbons into hydrocarbon fluids.

[0021]Another embodiment of the invention includes a method for heating a subsurface formation using electrical resistance heating. The method may include providing a substantially vertical first wellbore located at least partially in the subsurface formation, and providing a substantially vertical second wellbore located at least partially in the subsurface formation and adjacent the first wellbore. The method may also include hydraulically fracturing the subsurface from the first wellbore to form a first fracture, and hydraulically fracturing the subsurface from the second wellbore to

Problems solved by technology

Kerogen is subject to decomposing upon exposure to heat over a period of time.

However, the practice has been mostly discontinued in recent years because it has proved to be uneconomical or because of environmental constraints on spent shale disposal.

Further, surface retorting requires mining of the oil shale, which limits application to very shallow formations.

While research projects have been conducted in this area from time to time, no serious commercial development has been undertaken.

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